In a pan over medium heat, crisp the pancetta until the fat is rendered, and it is golden, about 2-3 minutes.
Make the dressing: Turn off the heat and remove the pancetta from the pan, keeping the renderings in the pan. Add the garlic to the pan with the renderings and stir together (the residual heat will cook it slightly). Whisk in olive oil, balsamic vinegar, lemon juice, red chili flakes, salt, and black pepper.
In a large bowl, toss together the Cannellini beans, cucumbers, tomatoes, parsley, dill, crispy pancetta, and the dressing from the pan.
Gently fold in the tuna, including the tuna olive oil from the can
Serve with lemon wedges for squeezing over salad if desired